I also read that Assassin Creed corrupted some user's HDD, but I don't know how far it's true.
I find it strange, but better keep one just in case.
Some games require that there is effectively a game (or any disc) in the drive.

I don't remember any "Emulate BD Rom" option. maybe it's in the newer version ? (4.0+)

Or maybe you are talking about "BD-ROM Emulation" (I guess that's the one you are referring to).
This setting is required to play games from HDD (internal or external). You don't need it if you play from burned BD media.

It's the option used to select the payload you want to use to patch your console's memory.
if you have BDEMU v2 and are using a custom firmware without native payload then you will have 3 choices : None / Default (PSGroove) / Hermes

Hermes payload is needed for few features, such as playing games with 4G+ files on external and caching only big files on internal.

I'm wondering how to get multiman to play a random song at startup from the tracks saved to my internal HDD. I know all about replacing the sound.bin to get the SAME track to always play on startup, but I'd like a random song to play at startup.

Somehow when I was updating my friend's multiman we got it to work by accident, we weren't even trying, it just all of a sudden started playing random songs at startup. I did my best to try and replicate exactly what we had done later to my own ps3 but couldn't get the same results.

It's been a year I didn't update my version on my console, I don't know what's new and how things changed.
I know there's a new mmOS (desktop like) mode which looks great.
I should try to update it.

Xflak, I see you just posted on PS3hax
I hope you'll get you answer.Maybe deleting the bin is enough to play mp3s randomly?

Good idea, I'll give it a shot and report back.

And about the mmOS, it is pretty sweet, I find myself using it all the time

edit:
deleting sound.bin didn't work, it just didn't play anything

edit2:
Solution
edit:

Go to 'Theme Audio' settings in second column on Mm and select 'MUSIC'. I usually QUIT Mm to save that setting (although needing to quit Mm to save settings may be an old feature but I still do it out of habit)

There you go. Mm will then select a random track from your MUSIC folder to play and you can test this by loading it again.

Hope this helps.

BTW if you do not have the 'theme audio' setting in the options column then press triangle and select 'advanced settings'. This should bring up all the settings for Multiman.

You don't need to run Lv2 patcher when you are using multiMAN.
Install BDEMU v2, it's doing the same thing as Lv2 patcher but automatically. MultiMAN patch the memory when you launch it.

BDEmu v2 even have more options than Lv2 patcher to play backups.
Lv2 patcher is still useful to do other things, but you shouldn't run both multiMAN and Lv2 at the same time. always reboot the console to clear the patches from memory.

I want to transfer Metal Gear Solid HD Collection on my PS3, but the psarc files are too large to send them at once with FTP server. Is there a way to split (not extract) the psarc files and reconstruct them in the internal HDD either via FTP or USB drive?

If it's too big by ftp it's certainly a problem on your FTP client (not working fine with files >2GB or 4GB)
You can try another client.

If you want to split the file, it's possible to do it on the computer, but it's easier if you process the full games folder, not just that file.

Use a spliter (there are few links in the tutorial on the first page), provides the game folder and it will split the files.
Then put that folder on your FAT32 HDD
use multiMAN and it will see that game and detects that it has split files. press Triangle > Copy > To internal HDD, and it will auto-join the split files.

The FTP client has no problem. It's my connection that's slow and I can't let it for the 12 hours it asks to send the 9GB psarc.

The other solution you suggest is interesting. I have a 14GB USB flash drive. Can I split the entire MGS HD collection into, let's say three parts, transfer them one-by-one and join them inside the console? As I mentioned, I'm specific to split the files, not extract them. Can't give it more space than the 21GB it already wants.

You could try to split only the 9GB file.
Then, instead of using the game manager to copy the game to the internal HDD, use the File manager and browse up to that split file on your external and select copy to the right place on your internal. It should automatically rejoin them.

If multiMAN doesn't rejoin them, but just copy them still in their split form, you can try with Comgenie's File Manager (that's the first homebrew which introduced that split form, and it's auto spliting-rejoining)

when split, they have an extension added .psarc.66601, .psarc.66602, .psarc.66603, .psarc.666xx etc.
when rejoined, that extension is dropped and you get your original file.

If you provide a folder instead of the file itself, most spliter will rename the folder with an underscore prefix "_game folder name".
that's how multiMAN recognize games with split files and ask to copy the game to internal before launching it.

But if you want only to copy the game folder manually to the internal HDD using the file manager, don't keep that underscore.